Go for A8 plus it has IP68 certification. NFC and MST which supports SAMSUNG PAY full version found on Flagships and It has dual 4g volte with cat11 faster 4g+ speed in oreo update..
A8 Star has Cat9 450Mbps for Download and 50 Mbps for uploadBut A8 Plus has Cat 11 600Mbps for Download and 75Mbps for upload and A8 Plus oreo version has DUAL TRUE 4G VOLTE but A8 star hasnt that.